Thermoformed clamshell food package with corner lid release feature

ABSTRACT

A one-piece thermoformed food package comprises a rectangular deep drawn base with a peripheral female rim channel and, connected to the base by a hinge, a lid having a peripheral male rim feature. In the corner of the base is a breakaway release feature which underlies a corner tab of the lid which is tucked into an inside edge of the female rim so that it cannot be accessed to open the package. When the user pushes up on the breakaway release feature, one or more frangible sections are broken and the lid corner tab is raised enough to open the package.

FIELD OF THE INVENTION

The invention relates to molded plastic containers suitable for packaging food products and more particularly to a container having a lid which can only be opened by performing a strategic manipulation in a predetermined location on the container.

BACKGROUND OF THE INVENTION

There are several plastic containers used for packaging food wherein a lid can, as a practical matter, only be opened by breaking off a section of a peripheral plastic structure which prevents access to an edge of the lid. One container of this type is thermoformed of a clear plastic and has an integral, hinged lid.

SUMMARY OF THE INVENTION

The present invention provides a container comprising the combination of a deep base and a shallower lid structure, the two being suitable for thermoforming. The container has a raised peripheral ridge around the open top and a recessed undercut which generally parallels the ridge but departs inwardly therefrom at a strategic location to form a flat deck. The lid has a peripheral, downwardly-projecting ridge structure that snap-fits into the undercut on the base to releasably secure the lid to the base. The interfitting relationship between the lid and base is such that the base ridge effectively surrounds the outside edge of the lid so that it is difficult to gain access to the lid edge for removal purposes. However, the lid ridge is truncated at a location that corresponds to the strategic base location to form a tab which overlies the lid deck. By exerting an upward force on the underside of the container deck, one can raise an edge of the lid enough to permit removal of the lid from the container. The deck can be formed to provide a breakaway portion which indicates that the lid may have been opened.

Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying photographs, the latter being briefly described hereinafter.

BRIEF SUMMARY OF THE DRAWINGS

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views and wherein:

FIG. 1 is a perspective view of a thermoformed “clamshell” container with integral, hinged lid embodying the invention;

FIG. 2 is a plan view of the corner detail;

FIG. 3 is a perspective view of a corner detail;

FIG. 4 is a perspective view of the corner detail being manipulated by a user;

FIG. 5 is a side section of the corner detail before breakaway;

FIG. 6 is a side section of the corner detail after breakaway; and

FIG. 7 is a plan view of an alternative breakaway feature.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

Referring now to FIGS. 1-6, there is shown a thermoformed plastic food container 10 comprising, in this case, the integral combination of a deep drawn generally rectangular container base 12 and a conforming lid 14 joined to the base 12 by means of an integral hinge 16 extending along one side. It is to be understood that the rectangular shape is merely exemplary and that other shapes are equally compatible with the inventive features described herein. The container base 12 comprises side walls 18 formed with half-moon shaped concavities 19 for rigidifying purposes and substantially flat end walls 20. The container 12 is completed by means of a bottom 22 which is also molded with a slight recess for rigidification purposes.

The container base 12 is generally rectangular with three rounded corners. One corner is truncated for purposes to be described. A raised, peripheral rim structure 24 is fully rectangular interrupted only by the hinge 16. An interior undercut recess 25 follows the contour of the rim 24 except at corner 23 where it is truncated, giving rise to a generally triangular deck 30 adjacent the truncated corner 23. Two strengthening grooves 32 are molded in the deck 30 on opposite sides of a breakaway tab 34 having three sides which are die-cut at 36 leaving only small frangible uncut sections 38 along the three die-cut sides. The fourth side; i.e., the side of the breakaway tab 34 closest to the peripheral edge feature 24 is uncut, thereby to create a hinge function as hereinafter described.

The undercut locking recess 25 is formed just inside of and generally parallel to the rim structure but, unlike the rim structure 24, runs inside of the deck 30 and the push-up tab 34. The lid 14 is similarly configured with an overall rectangular shape and has a male ridge structure 40 which mates with the female undercut 25 of the base to “lock” the lid 14 to the base 12 by pressing the structure 40 resiliently down within the undercut 25 until the entire lid structure snaps into place. A truncated portion 42 of the lid rim cooperates with the corner structure of the base to the extent that it runs inside of the tab 34. However, a thin, resilient edge tag 44 of the lid 14 lies outside of the corner 42 to overlie the push-up tab 34 and the deck 30 to the extent that it abuts up against the inside edge of the upstanding rim structure 24 tightly enough to prevent access to an edge of the edge rim 27 at any point. The tight fit between the rim edge 27 and the inside surface of the rim structure 24 such that no point of the lid edge can be reached except possibly with the use of a sharp tool.

To open the package, the user places a finger on the underside of the tab 34 as shown in FIG. 4 and pushes it up sufficiently to break the uncut anchor areas 38. The upward force is projected through the push-up tab 34 to the lid corner tab 44 exposing the edge of the lid to the point where the user may engage it with the edge of his or her thumb to gain access to the content of the container, as shown in FIG. 6.

FIG. 7 shows an alternative embodiment in which a push-up tab 50 is generally circular in configuration with two crossing die-cut lines having uncut frangible portions 52 adjacent the point of intersection between the two die-cut lines. Again pushing up on the breakaway section 50 from below breaks the frangible sections 52 and transmits the lifting force through to the corner tab 44 of the lid allowing it to be lifted up relative to the base 12 to gain access to the contents of the container. The breakaway tab 50 is in a truncated corner like the embodiment of FIGS. 1-5.

Although shown with respect to two illustrative embodiments, it will be understood that the breakaway portion can be formed in still other configurations including those involving a partial breakaway as well as those in which a piece or section of the corner deck is completely broken away. The former has the advantage of eliminating a scrap piece. While FIG. 5 shows the breakaway tab 34 of the base container flush against the lifting tab 44 of the lid, it is also possible to form a slight lip or recess in the tab 34 which creates a gap between the elements 34 and 44, thereby insuring that the breakaway tab must be pushed far enough to break the frangible anchor section 38, 52 before the lid tab 44 is raised enough to allow the lid to be opened.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law. The material of construction can be any of several polymers, including a clear acrylic plastic which allows the contents of the container to be seen through the lid and base. 

What is claimed is:
 1. A plastic container comprising: a container base having at least one corner, peripheral rim structure extending around said corner, and a corner deck within said rim structure; a lid conforming to said container base and attached thereto and having a corner tab which, in use, overlies the corner deck and interiorly abuts said base rim structure to inhibit access thereto; and a breakaway section formed in the corner deck to permit a force to be applied through said section to the corner tab to lift said corner tab and substantially simultaneously at least partially separate said section from said deck.
 2. A plastic container as defined in claim 1 wherein the container base and lid are integrally thermoformed so as to be attached by means of a hinge.
 3. A plastic container as defined in claim 1 wherein the breakaway section is essentially rectangular and is die-cut relative to the deck leaving at least one frangible section which is broken away when said force is applied to said section to lift corner tab.
 4. A plastic container as defined in claim 3 further comprising a pair of strengthening grooves on opposite sides of the breakaway tab.
 5. A thermoformed plastic container as defined in claim 1 wherein the breakaway section is essentially round and is die-cut so as to be divided into generally symmetrical sections when an upward force is applied thereto.
 6. A method of opening a molded plastic container of the type having a base and a lid which attaches securely to the base in such a way as to tuck an edge of the lid against a peripheral rim of the base comprising the steps of: pushing up on a breakaway tab formed in a corner of the base underlying a conforming corner of the base underlying a conforming corner of the lid sufficiently to at least partially fracture a portion of the tab and lift a corner of the lid sufficiently to expose an edge of the lid for removal purposes. 